1. Field of the Invention
The present invention relates to an image processing apparatus for processing a video signal to generate image data suitable for a recording apparatus such as a printer.
2. Related Background Art
FIG. 1 is a block diagram of an image processing apparatus employed as a capture board for image fetching in a conventional printer, wherein various circuit blocks are provided on a same circuit board.
Referring to FIG. 1, an input unit 12 receives an analog composite video signal from an image taking equipment such as a video camera or a VCR, for provision to a video signal processing unit 13 which demodulates the composite video signal to generate R, G and B signals. The R, G and B signals are converted by an A/D converter 14 into digital signals, which are temporarily stored in a RAM 15. A synchronization processing unit 16 separates synchronization signals from the video signals and provides the synchronization signals to the A/D converter 14, for synchronizing the sampling timing thereof.
A processing unit (microprocessing unit: MPU) 17 processes the R, G and B data of the RAM 15 according a program stored in a ROM 18, thereby generating image data matching the recording format of a printer, and sends the data to the printer through an external interface 19. The MPU 17 also controls other circuits based on the program.
A switching controller 20, for switching the bus line in synchronization with the synchronization signals, for enabling the use of a common bus of the present apparatus for digital signals by various circuits, is composed, for example, of an ASIC (application specific integrated circuit such as a gate array. There are also shown a data bus 21 and an address bus 22.
In the image processing apparatus of the above-mentioned configuration, the R, G, B signals of the RAM 15 are converted by the MPU 17 into image data matching the recording format of the printer. For example, in case of process printing, the R, G and B signals are converted into data of complimentary colors, having gradation in cyan, magenta, yellow and black colors.
Also in case of ink jet recording, which can only perform a binary representation, there is executed a process providing a pseudo gradational representation, corresponding to the multi-value representation of the input video signals.
FIG. 2 is a perspective view of a recording unit of a printer of the ink jet recording system, wherein a recording sheet is advanced by a roller 24 and recording is-executed thereon by a recording head 25. The recording head 25 is provided with a plurality of nozzles along the sub scanning direction, and forms an image on the recording sheet 23 by selectively discharging ink from the nozzles according to the image information, while moving in the main scanning direction. A cap 26 is provided for preventing the ink from drying in the nozzles.
Also, an animation image may be entered from home-use computer game machines as the input signal source. In such case, the input image is developed once in a memory, but the amount of image information per frame of the cathode ray tube is significantly large and the capacity of the existing semiconductor memory is not large enough for this purpose. In inexpensive game machines, the effective image frame is made narrower to optimize the memory capacity.
The conventional image processing apparatus is designed to generate image data, for example of cyan, magenta, yellow and black colors, matching the recording format of the printer by processing the input video signals in the above-described manner, and always executes same image processing without any particular consideration of the content of the image. For this reason, the quality of the output image may be deteriorated for some image components.
More specifically, for a natural image, important factors are luminocity and color gradation, while, for an animation image, the sharpness of the image contour portions is important. Thus, an image processing advantageous for one image may be disadvantages for the other. For example, with image processing advantageous for an animation image, the natural image will lose gradation and will appear like a water-colored painting. On the other hand, with image processing advantageous for the natural image, the animation image will lose sharpness at the contour portions and will appear as an unsharp image.
Also in case the effective image frame is made narrower by utilizing a computer game machine as the input signal source, there results a black blank period in addition to the flyback period in the scanning operation. In case of display on a cathode ray tube, such blank portion at the corners is usually not conspicuous because of the structure of the cathode ray tube, but, in case of the capture board for the conventional printer, such blank portions are directly recorded on the recording medium, thus resulting in an unpleasant impression on the reproduced image.